1. Field of the Invention
The present invention relates to a bicycle hub mounted to a bicycle frame.
2. Background Information
Official Gazette for Kokai Utility Model No. S52-60062 discloses a conventional bicycle hub installed in the central portion of a wheel of a bicycle comprises a hub axle, a hub body and a pair of bearings. The hub axle is non-rotatably mounted to a frame of the bicycle (for example, to a front-fork). The hub body is coaxially coupled to the hub axle so that the hub body is disposed radially outwardly with respect to the hub axle. The bearings are configured and arranged to support the hub body so that the hub body can freely rotate around the hub axle. The outer peripheral surface of the hub axle includes a pair of male screw sections in axial ends thereof so that the hub is mounted to the frame by a pair of nuts that are screw on axial ends of the male screw of the hub axle. The bearings are angular-type bearings. Each of the bearings is provided with an outer ring, an inner ring, and a plurality of rolling components. The outer ring is disposed along an inner peripheral surface of the hub body and includes a ball receiving surface. The inner ring is screwed into the hub axle and includes a ball pushing surface. The rolling components are disposed between the outer ring and the inner ring at predetermined intervals in a circumferential direction of the hub.
The inner portion of each of the bearings is filled with grease in order to make the rotation of the bearings smooth. The ball receiving surface of the outer ring is arranged as a concaved surface that faces toward a generally axial outward direction of the hub axle. The ball pushing surface of the inner ring is arranged as a concaved surface that faces toward a generally axial inward direction of the hub axle. The angular-type ball bearing installed on the hub is designed to maintain a certain degree of clearance or gap between the radial innermost peripheral surface of the outer ring and an outer peripheral surface of the hub axle. Moreover, a sealing component is coupled to an outer axial direction of the bearing. Therefore, the bearing is designed so that the grease does not leak towards the outer axial direction of the bearing.
However, since there is the clearance between the outer ring and the hub axle in at an axial inner position of the bearing, the grease filled within the bearing occasionally leaks towards the inner axial direction of the bearing. Especially when the hub includes the male screw section is formed in the same screw direction along the entire surface of the outer peripheral surface of the hub axle, the male screw acts like a pump due to the rotation of the wheel (i.e., the rotation of the outer ring of the bearing) relative to the hub axle. Consequently, the grease flows out form the bearing toward the inner axial direction of the hub axle. For example, in a case in which the male screw is a right-handed screw, in the bearing on the right side as viewed from the rear side of the bicycle, when the wheel rotates in the direction of travel, the grease tends to flow out toward the inner axial direction of the hub axle. When the grease flows out from the bearing toward the inner axial direction of the hub axle, the grease tends to travel toward a relatively larger space behind the outer ring and retained in that space due to the centrifugal force. In such a case, the amount of the grease in the bearing becomes insufficient, and rotation of the wheel deteriorates.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle hub. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.